Lead wire construction



June 13, 1939. K MATTHlES E;- AL 2,162,489

LEAD WIRE CONSTRUCTION Filed March 9, 1938 Fig.

WlTNESSESI INVENTOR s h ies and aiented June 13, 193

Schaft, Siem ll a dt, Berlin-Friedemann, Ge

assignors to Siemens & l. near ,v

corporation of Ge ke, Aktie lin, Gc a application ch 9, resa serian No.isaaoo ma@ may s, 19st The invention relates to sealing-in wires andespecially sealing-in wires for discharge tubes.

operating on short and ultra-short waves.

An object of the invention is to provide a sealing-in'wire that will nothave the high losses of magnetic material when used with short waves andon the other hand will have an expansion i coefficient suitable forsealing with the glass casing or the glass utilized as vacuum-tightsealing mate- 'iial around the wire with casings of other mate- Otherobjects and advantages of the invention will be apparent from thefollowing description and drawing, in which:

Figure 1 is a cross-section through the press of a discharge tubeillustrating the preferred embodiment of the invention; and

Fig. 2 is an elevation with parts in cross-section of a press of adischarge tube illustrating another 2@ modification of the invention.

The sealing-in wires for discharge tubes are usually made of certainmaterials, such as, for instance, alloys of iron or chromium, which aremagnetic and which cannot be used, therefore, in

the case of tubes that operate on short and ultrashort electric waves,because in this case their use would involve high losses. On the otherhand, non-magnetic materials, such as copper, which have been proposedfor the purpose just men- 39 tioned have the disadvantage that theirexpansion coefficients differ too much from the expansion coeilicient ofglass, so that if sealing-in leads in the form of wires or rods made ofsuch a material are used, diiculties will be encountered when the 35seals are made, while afterwards the seals may start to leak.

The present invention covers an alloy whose expansion coeicient is aboutequal to the expansion coefficients of the ordinary commercial grades 40of glass, while on the other hand the alloy is practically non-magnetic.In line with the invention, .erjsealing-in wire for short-Wave dischargetubes is made of a material obtained by alloying iron or nickel eitherwith tantalum, or with columbium 45 (also called niobium) or withtantalum and columbium, the iron or nickel content, or the content ofiro'n and nickel in combination, being not higher than It has been foundthat the expansion of an alloy of this kind is such that the 50 alloy isa very suitable material to be sealed in by fusing in ordinarycommercial grades of glass. The alloy should contain a smaller or largeramount of nickel or iron, depending on the grade of glass. This contentof iron or nickel should 55 not exceed 30% in order to obtain a materialhav- (Ul. 25d-27.5)

ing non-magnetic properties. It has been found that a content of 1li-20%Ynickel is especially advantageous for ordinary grades of soft glass,because in this case the expansion coeicient of the metal is mostclosely equal to that of the glass. 5 But the content of iron or nickel,in percent, should never be less than 5%.

In those cases where it should not be possible to make the expansioncoemcient of, the metal .j exactly equal tol that of a given grade ofglass by 10 properly choosing the iron ornickel content, it may beadvisable Vto use a sealing-inwire in the form of a rod-shaped core ontowhich has been shoved a tube-shaped sheath having a length correspondingto that of the fused seal. The ends l5 of this sheath must be joined tothe core, for instance, by soldering or by welding; this will produceproper seals at these ends. The sheath should be so thin that afterbeing fused-in it can yield under the influences of the stresses set upin 20 the glass, while on the other hand the core inside the sheath cancontract freely without endanger.- ing the permanent tightness of theseal. 1

' If the sealed-in lead should be called uponcto carry, in addition to ahigh-'frequency currenta 25 strong current of normal frequency 50 or 60cycles say, it would be advisable to use a lead in the form of a tubemade of an alloy covered by this invenf tion into which has been shoveda core of copper. t An example of such a lead-arrangement is repre- 30sented in Fig. 1 on the drawing. Here the tube made of non-magneticalloy described in this specication is designated by l, and the coppercore by 2. Air-tight joints between these two parts can be made in anysuitable manner. The use of this copper core offers the advantage that ahighly conductive lead is obtained, a point of great importance if thelead must carry heavy currents, While the tube-shaped sheath of thelead, which is made of an alloy covered by this 40 invention, is verywell suitable for sealing-in purposes insofar as the expansiveproperties of the material are concerned.

The construction in Fig. 2 makes it possible to use any non-magneticmaterial, and especially for sealing-in leads in the form of rods forhighfrequency tubes. In line wtih the present invention, a sealing-inlead for electric discharge Vessels, and especially for dischargevessels that must operate at high frequencies, consists of a tube-shapedouter part into which has been shoved with some clearance a rod-shapedor tubeshaped core, whereupon the clearance space between core andsheath has been closed by soldering the ends of the latter to the core.The effect which application of the method covered by this inventionwill have will be better understood if reference is made to the drawing.It shows the stem Il ofatubeinto whichapluralityofleadshavebeensealedbyfusion. Rachoftheseleadsconaistsofacoreliofwirewhichissurroimded by a tube-shaped sheath I8 overthe entire lenzth of the lead that is fused into the Klass. The externaldiameter of the rod-I2 and the internaldiameter of thesheath i3 havebeen so chosen that the sheath can be shoved onto the rod withoutditlicultm 'Ihe clearance space the one end by means of'solder Il otherend by means of solder Il. 'nais double seal is very reliable for thesolder will be drawn into the clearance space between the bodies i2 andI I. due to the "slit-effect, and for this reason the opening wm be nnenup m quite sausfactory manner. At the same time the little tube I3willbe supported by therod l! at the soldered Joints.

deformed. This is an advantaae not shared by other known methodsotsealing in leads by fusion, because in the latter cases there is fromthebeginninganair-sapbetweenthecoreand the sheath surrounding the core.If then, after thesealhasbeenmade,therodcoolso,the leadwillcontraetmorestronglythanthealass,

if it is yassumed thatcopper is being means that it the lead should havevidedintheformofa solidrod,stressesismade,butthisclearancespaceisnotatall objectionable.

All diiiiculties encountered as aJconsequence of the diilerenee betweenthe expansion eoeilicients of-themetal andtheglasswillbe eliminatedby,wplyinsthemethodcoveredbythepresentinvention. Therefore. in makingsuchseals. tbe metalpartstobefusedintothellasscanbemade of-a materialchoaen/ velyonthe'basiaof 1u conductivity and of 1th mnesmntom. nomthisviewpoint, averysuitable material is copper. roritisknownthachummm-trot adhering very tiahtlytozlasa.

AConcerningthe choiceofthe thickness-ratio of rod and sheath, thestatement can be made that :ummmfoundtobeaclvwntureousimmune,`

inventionV may have many applications besides` the particular useillustrated. No limitations are accordingly intended on the followingclaims except as are necessitated by the prior art.

We claim as our invention:

l.A sealing-in wire for tubes formed fromva sheathofanalloyofb to 30%from theiron group and the remainder from the sroup consisting oftantalum anzi columbium and'a conductive core for said sheath. Y

2.Asealininwireiortubiormedtroma sheathofanalloyofimtom fromtheirona'roup and the remainder from the Iroup consistingoftantalumandeolumbium andra conductivecoreofcopperforaaidsheath.

.8.Asealing-inwirefortubformedi'roman alloyoiwhichimtow'isametalselected fromthegroupconaistingofironandnickeland .theremainder is from the zroup consisting of KURT m'rrams. mmm' GANswmn'r.-

